Human variability in behavior and mental traits will be studied and analysed with a view to determining how much of it is due to genetic influences, and where possible the mode of genetic action determined. New statistical techniques will be devised for this purpose, and applied both to data that have already been collected and to data that will be collected with the special purpose of identifying major genes for such traits. The possible existence of such major genes will be demonstrated by pedigree analysis, and by a search for linkage relationships between such genes and marker genes in blood. This will lead to a more complete understanding of the determinants involved in the development of human bevavior patterns and mental traits. BIBLIOGRAPHIC REFERENCES: D.C. Rao, N.E. Morton, R.C. Elston and S. Yee, "Causal analysis of academic performance", Behavior Genetics 7, 1977, 147-159. V.L. Tanna, G. Winokur, R.C. Elston and R.C.P. Go. "A linkage study of pure depressive disease: the use of the sib-pair method, in press, Biological Psychiatry, 1977.